Support for the Christian Democrats fell 0.4 percent and the Sweden Democrats gained 0.9 percent compared with figures from January, leaving both parties with equal levels of voter support.
Not since January 2005 has support for the Christian Democrats been so low, as measured by Synovate.
The February Synovate poll, published in newspaper Dagens Nyheter (DN), shows combined support for the Social Democrats, the Greens, and the Left Party at 55.3 percent.
The four parties making up the Alliance government register support of 40.3 percent.
The different between the two blocks has fallen from 20.6 percent to 15 percent since January.
All of the other changes since the January survey are within the margin of error.
The Social Democrats have lost support in large cities and suburbs, said Synovate analyst Niclas Källebring to DN.
With the exception of the Christian Democrats, the governing parties each gained 0.9 percent compared with figures from January. Support for the Moderates is now 22.6 percent, with the Liberal Party at 7.8 percent and the Center Party at 6.8 percent.
The Social Democrats lost 3.1 percent, bringing their level of support to 43.7 percent.
The Left Party dropped 0.5 percent to land at 5.1 percent, while the Greens gained 0.4 percent, bringing the party to 6.4 percent overall.
The number of uncertain voters is also large, at 17 percent of the 1,962 people who were interviewed in the two week spanning February 14-27.